Breast cancer is the leading cancer diagnosis in women and second most common cause of women cancer deaths. Although mortality has decreased and incidence has remained steady, persons diagnosed with late Stage disease have dismal survival rates. Hence, the need for therapies with the ability to prevent cancer altogether. The objective of this project is to determine if IL-12 induced functional conversion of tumor associated macrophages from anti-inflammatory and tumor supportive to pro-immunogenic and anti- tumorigenic can be extended for therapeutic exploitation. The mice 4T1 mammary carcinoma with lung metastases model will be employed to accomplish the objective and achieve the specific aims of this project. Specific aim 1 will examine the immune cells and cytokines that contribute to the maintenance of the IL-12 induced pro-immunogenic functional conversion of the macrophages. Two approaches will be used in this aim. First, the IL-12 response of scid mice which are T and B cell deficient will be compared with NK depleted scid mice. Secondly, the role of IL-18 and IFN-y in the maintenance of the IL-12 induced conversion will be assessed by neutralizing these cytokines with anti-IFN-y or anti-IL-18. In specific aim 2, the ability of IL-15 and IL-18 to extend the pro-immunogenic status of tumor associated macrophages will be examined by injecting mice bearing 4T1 tumors with the encapsulated IL-12 alone and then injecting the mice subcutaneously with encapsulated IL-15 or IL-18 one to four days later. Specific aim 3 will determine if the extension of the IL-12 induced pro-immunogenic window enhances the efficacy of a tumor-dendritic cell vaccine via immunization of 4T1 bearing mice with a 4T1-dendritic cell fusion vaccine in combination with encapsulated buffer or encapsulated IL-12 alone or in combination with other cytokines as determined by specific aim 2. Analysis for each of our aims will include q-rt-PCR for various anti-inflammatory and tumor supportive, as well as, pro-immunogenic and anti-tumorigenc factors, ELISA for serum IFN-gamma, measurement of cytoplasmic levels of IFN-gamma, perforin, and granzyme B, perfusion assisted weight and volume measurements for the primary tumor, perfusion assisted quantification of lung metastases, and anti- IFN-gamma and CD71 labeling for measurement of number of infiltrating leukocytes. By exploring the effects of IL-12 on tumor associated macrophages, we may gain a better understanding of how cytokines and macrophages interact for tumor maintenance and progression.